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  • Light EQ


    Hello, I notice something bizarre in the use Light EQ. When using Light EQ in the development mode (automatic), the result is different than if used in edit mode - always in automatic mode. In edit mode, the darker function always remains at zero. Is this a bug?

  • #2
    Sorry this response took so long to answer, but I had to think about the question a bit. It's a good question, but I personally don't think I'd be able to call it a "bug". The following is an EXTREMELY simplified explanation to a somewhat complex question.

    Remember, the whole way you "edit" a photo is significantly different in the Develop tab than it is in the Edit tab. Depending on your camera and it's raw capability, the develop tab has access to all the raw information stored in the raw image. That means the raw image stores enough exposure information to provide a 'correct' exposure for anywhere from +/- 2 to 7 exposure value 'stops' and an almost unlimited ability to alter white balance to however you like it.

    That means Light EQ, and the other tools in the Develop tab, that affect exposure, tonality, and color, have FAR more information on which they can factor into their editing algorithms.

    When you send an image to the Edit tab whether raw or a bit mapped file like a jpg, you lose all of that raw flexibility. The raw file's exposure,tonality, and color is frozen at the point at which it looks like when you send it to the edit tab. You LOSE all the flexibility inherent in raw, and are now limited to whatever pre selected exposure tonality and color you sent to the edit tab. You now have to work within that limited set of of options.

    So in that sense, the Light EQ probably SHOULD provide different results in the Edit tab than in the Develop tab. It has less information to work with.

    Now that brings up the question, "should editing a jpg or tif file in the develop tab provide different results from the edit tab, since both are working with the limited exposure, tonality, and color options inherent in bit mapped (i.e. not raw) photo files?" If both tabs shared the same programming algorithms and logic, then they should be the same. BUT, do they share that same logic? I don't know. I mean, the develop tab has to be able to recognize a raw file when it encounters it, and it needs to be able to recognize that jpg too. Then it needs to have the ability to be able to tap into the extra info for the raw but not the jpg, make the changes, and then instead of changing the photo itself, SAVE that data for retrieval in the sidecar file.

    Does all that extra logic in the Develop tab change what is possible when editing a bit mapped file? Does it make certain programming options more, or less, likely to happen? I don't know, users don't get access to software publisher's proprietary source code.

    I personally would say, the anomaly is a valid artefact arising from the inherent differences between raw development and bit mapped editing.

    Sorry the response is so wordy, and not a quick answer, but the subject just doesn't lend itself to that sort of thing.
    Last edited by Glen Barrington; 04-01-2017, 10:02 AM.

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    • #3
      I remain a bit skeptical about this explanation which consists of processing a raw in developer mode and which will lose information in edit mode as a jpg. However, in my example, I have processed .jpg files. If, however, developers come to the site for a more convincing explanation, it would be nice! Thank you for your explanation.

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      • #4
        I've done enough experiments to know that color profile greatly impacts the information in any JPG or TIF file (RAW files do not include a color space inside the file). Also, with the nature of JPG, a part of the compression algorithm does interact with color space options. Thus, I would second Glen's explanation as a possible cause of difference.

        Knowing there is sometimes more than one thing to look at, I just tried an experiment...
        ​Started with a Nikon NEF (RAW) file.
        ​a) ​Edit Mode > Light EQ > Auto: Slider bars were moved per ACD algorithms (Result: 16,9,4)
        ​b) ​Develop Mode > Light EQ > Auto: Slider bars were moved per ACD algorithms (Result: 32, 27,12)

        ​Slider values selected were -very different-

        I then converted the same NEF (RAW) file to a TIF (ProRGB colorspace)
        ​a) ​Edit Mode > Light EQ > Auto: Slider bars were moved per ACD algorithms (Result: 16,9,4)
        ​b) ​Develop Mode > Light EQ > Auto: Slider bars were moved per ACD algorithms (Result: 16,9,3)
        Slider values were -very close-

        INTERESTING!!

        ​I am not sure what this means yet. I now REALLY wonder what ACDSee does when you open a RAW file in Edit Mode! A Developer could really help!!
        ​I will think about it, but I am not sure of a good experiment that can tease out the actual operational difference.... Thinking.... thinking.... thinking....



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        • #5
          You are correct, Gus! I neglected completely the color profile issue.

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